Telephone receiver



March 14, 1944. BALDWIN TELEPHONE RECEIVER Filed April 28, 1941 I I EINVENTOF? Patented Mar. 14, 1944 f UNITED STATES PATENT OFFICETELEPHONE. RECEIVER Nathaniel Baldwin, East Mill Creek, Utah ApplicationApril 28, 1941, Serial No. 390,772

6 Claims.

The present invention relates to telephone receivers in which themovement of a vibrating armature of magnetic material is transmitted bya link or connecting rod to a diaphragm which may be non-magnetic. Theinvention is particularly an improvement on my former inventions as setforth in Patents Nos. 957,403, 1,153,593, and Re. 16,887.

The object is to provide an instrument of this class which is smaller,lighter, simpler, cheaper to manufacture, more efiicient, and morerugged and durable than the structures formerly disclosed.

I attain this object by a new design of polepieces and magnets, a newmounting of the armature in a moulded spool, a special design ofdiaphragm, and a new design of terminal connections.

In the drawing Fig. 1 is a rear view of the instrument with the bottomof the shell cut away; Fig. 2 is a section along the line 8, 8 of Fig.1; Fig. 3 is a section along the line 9, 9 of Fig. 1; Fig. 4 is asection along the line 16, ID of Fig. 1; Fig. 5 is an enlarged portionof Fig. 3; Fig. 6 is a section along the line I i, l I of Fig. 5; andFig. '7 is a section of the diaphragm before installation.

In the several figures of the drawing numeral l2 designates the shell orhousing for the mechanism which is provided with an earpiece or cap l3.Between the edge of the shell I2 and the cap 13 is clamped the baseplate M which is provided with a seat for the diaphragm I5 and to whichthe other parts of the instrument are bolted.

The spool l6, preferably made of Bakelite or other insulating materialis held in place between the limbs of the U-shaped pole-pieces ll. Thesepole-pieces are provided with extensions at either side, and betweenthese extensions the two magnets l8 are inserted and clamped firmly inplace by bolts l9. These magnets may be made in the form of tubesthrough which the bolts [9 pass, or they may be made with grooves in oneside as shown in the drawing, and within these grooves the bolts l9extend from the extensionsof one pole-piece through the extensions ofthe other polepiece and are tapped into the base-plate I4. The magnetsare made of very powerful magnet steel composition and are so magnetizedthat the flux passes straight through the magnets from the extensions ofone pole-piece to the extensions of the other, and in the same directionthrough both magnets. So the magnetic circuit is divided between the twomagnets and otherwise it is divided between the limbs of the polepieces.

The spool l6 containing the actuating coil 20 is held in place by thepolepieces. l1 and carries the vibrating armature 2|. This armature ismounted within the spool l6 upon a fulcrum which I designate as a crestfulcrum to distinguish it from the suspension wire fulcrum as used in myformer structures. This crest fulcrum may consist of a point or pointsupon which the armature oscillates, or it may consist of one or morerocker-shaped supports 22 as illustrated in the drawing; and to keep thearmature and the rocker-shaped crest fulcrum in proper relativepositions thin, narrow, and flexible strips of metal 23 may be sealed aswith solder or any other means at one end to. the armature and at theother end to the rocker-shaped fulcrum. To insure continuous contact ofthe armature and fulcrum a spring 24 which may also be rocker-shaped maybe used within the spool so that the middle part of the spring will bearagainst the armature. The combined efiect of the rocker-shaped spring onone side of the armature and the rocker-shaped fulcrum on the other sidewill be to center the armature within the spool when it is under nostrain from without and to resist displacement of the armature with aforce which will be very slight when the displacement is small but whichwill increase with the displacement much more rapidly than thedisplacement increases. The resulting stabilizing effect. upon thearmature is very desirable because normally the armature should be veryeasily displaced in order that the telephone might be sensitive, but asthe armature approaches the pole-pieces the magnetic attraction ismultiplied, and unless the resistance to displacement is also multipliedthe magnetism may overcome the elastic means and bring the armature intocontact with the. pole-pieces and hold it there and render theinstrument inoperative. The rocker-shaped fulcrum and rocker-shapedspring are safety factors. Longitudinally of the armature depressionsare made in the armature to allow the rocker-shaped fulcrum 22 to bearon surfaces which lie in a plane passing through the center of thearmature at the ends, said plane being central to the armature at theends with respect to its thickness. Similarly, a depression on thereverse side of the armature allows the rocker-shaped spring 24 to bearon a surface which lies in the same plane. The result is that slightmovements of the armature will not cause to a diaphragm in such way thatthe diaphragm will not normally be under a strain and the connecting rodwill push and pull on the diaphragm in its operation. If it is desirablethe rockershaped spring 24 may be modified in shape so as to putastrain' on the diaphragm, in which case the connecting rod may exert apulsating force on the diaphragm in one direction 'only.

. The force will either be a pulsating push or a.

pulsating pull.

As illustrated in the drawing the rockershaped spring 24 is shaped so asto assist in keeping the armature in its central position, and while thediaphragm I is so shaped that it needs to be put under a strain to holdit in proper shape for eflicient operation the balancing force againstthis strain is provided by the spring 25 which is seated. at one end ina socket in the armature and at the other end in a socket formed in thepolepiece l-I.

Before installation this diaphragm l5, Fig. 7, which is made of thincorrugated metal is slightly dished in one direction, and wheninstalledthe strain produced by the counterbalancingspring 25 renders it morenearly straight and in proper position for operation. 'In assembling,the spring 25, properly adjusted, is put in place and then the diaphragmwith link 28, washer 29, and nut is put in place, and the nut 30 isscrewed up until the armature -2l is centered between the polepieces.With this arrangement the diaphragm does not have to be clamped at itsperiphery.

The spool I6 is provided with metallic inserts 3| to-which the ends ofthe coil 20 are soldered and the electrical connection to these insertsis made by jumpers 32 which are also connected to the spark-gapterminals 33. These sparkgap terminals arefirmly bolted to the terminalblock by bolts 34 and nuts 35 and thecord terminals 36 are also clampeddown upon the same bolts by nuts 31. The'terminal block 38 is firmlybolted to the base plate l4 by bolts 39. =A curved aperture 40 throughthe terminal block 38 receives the'cord 4| after it enters the shellthrough the opening 42; The two separate conductors of the cord-42 bendover the edge of the terminal block 38 making a loop and having allnecessary resistance to a pull onthe cord.

For this reason there is no need of a tie-string to be used in thisinstrument.

I claim: .1. A telephone receiver comprising an actuating coil, U-shapedpole-pieces inclosing said coil, an armature. surrounded by said coiland acted upon by said polepieces and balanced upon a .ture to saiddiaphragm.

3; A telephone receiver comprising a magnet, polepieces for said magnet,an armature acted upon by said polepieces, a coil to actuate saidarmature, a crest fulcrum for said armature, a

depression in said armature to receive said crest fulcrum, arocker-shaped spring to hold said armature in contact with said crestfulcrum, a diaphragm, and means to transmit the movement of saidarmature to said diaphragm.

' 4. A telephone receiver comprising a magnet, polepieces for saidmagnet, an armature acted upon by said polepieces, a coil surroundingsaid armature to actuate said armature, a rockershaped crest fulcrumwithin said coil for said armature, a depression in said armature toreceive said rocker-shaped fulcrum, a diaphragm which is dished beforeinstallation and more nearly straight after installation and connectedto one end of said armature, and a spring acting upon the other end ofsaid armature and adapted to hold the diaphragm in straighter form andto co-operate with said diaphragm to stabilize said armature.

5. A telephone receiver comprising a magnet, an armature, an actuatingcoil surrounding said armature, U-shaped polepieces for said magnet andsurrounding said coil and acting upon said armature, a crest fulcrum forsaid armature within said coil, a rocker-shaped spring within said coilto hold said armature in contact with said fulcrum, a depression in saidarmature to receive said rocker-shaped spring, a diaphragm, and means totransmit the movement of said armature to said diaphragm.

6.'A telephone receiver comprising a magnet, an armature, an actuatingcoil surrounding said armature, U-shaped polepieces for said magnet andsurrounding said coil and acting upon said armature, a depression insaid "armature to receive said rocker-shaped crest fulcrum, arockershaped spring within said coil to hold said armature in contactwith said fulcrum, a depression in said armature to receive saidrocker-shaped spring, a diaphragm and means to transmit the movement ofsaid armature to said diaphragm.

NATHANIEL BALDWIN.

